FAQ - Plastic Ductwork for aggressive environments

Being a metal ductwork with 20 years of experience, we acknowledge that for many of our clients plastic ventilation with chemical resistance properties is a novelty, therefore we prepared a short FAQ:

Are circular plastic fittings male and ducts female like is the case for metal spiral ductwork?

NO - plastic fittings are female and ducts are male. The diameter given in the catalogue is the external dimension of the duct.

Please explain the different joining methods?

Plastics are joined mainly by welding; glueing by means of special adhesives, which dissolve the bound surfaces, is possible only in the case of PVC. Several joining techniques are applied, e.g. gas welding using the welding wire. This is an ideal solution for fitters because of the reasonable price and low weight of these devices. Extrusion welding is a more advanced and efficient method. Owing to this advanced method, it is possible to create very thick welds during a single run - it is possible to weld the material with the thickness up to 40mm. Extrusion welders extrude the adhesive, which is applied by the welding shoes to the joined surfaces plasticised with hot gas.

Are there any other joining methods?

YES, there are e.g. flange connection. FLSF flanges are on offer. A gasket made of EPDM, eg PVC-GASK, will be needed for flange connections.

What kind of welding device can you recommend?

For example, Autotherm3 by Wegener welding gun set (photo above). Since its plastics are niche market in the ventilation industry, we offer our clients welding equipment for rent. In the offer, we also have welding wire, glue for joining PVC fittings.

Wegener welding gun set.

Is it possible to glue this kind of installation?

YES - but only PVC up to ø250.

What is the standard plastic duct length?

The circular ducts are delivered in 5m length sections - this is the standard length. But, if needed we can cut them into 1m and 2.5m sections. Rectangular ducts in the standard are manufactured in 4 standard lengths: 1m, 1.5m, 2.5m and 3m, on a special request we can manufacture any size of the ductwork.

What is the fire resistance class of the chemically resistant ventilation system?

PVC - class B - s3 d0 (according to DIN 13501-1)

PPs - class B1 (according to DIN 4102-1)

Do the materials differ in colour?

Yes, they do. To better distinguish the materials that in their natural form, they are generally semi-transparent, we use standardized colours.

What materials and diameters do we have in stock?

In the warehouse, we keep PVC and PPs in diameters ø110-450: pipes, couplings, 90 ° and 45 ° elbows, tees, end caps, dampers, flanges, symmetrical reducers. The waiting time for the remaining elements is 2-3 weeks. As far as rectangular ductwork is concerned it depends on the order.

Circular ventilation ductwork made of plastics

Can plastic ventilation ducts be laid in the ground?

NO - these are thin-walled elements intended for suspended installation.

Can plastic ducts & fittings be stored outside?

Unfortunately, they can not be stored outside. Elements exposed to atmospheric factors such as solar radiation initiates or significantly accelerates the ageing process of materials. This process is caused by a chemical reaction taking place inside the material, which leads to changes in its internal structure. Internal transformations cause significant changes in the technical parameters of the plastic: it is less elastic, more fragile, easier to crack, breaks, it loses transparency, yellows, etc. The same applies to the temperature at which plastic components are stored. Brittleness temperature - this is the temperature at which the material loses its plastic properties and becomes fragile. It is given most often in degrees Celsius. For PVC, it is 0 degrees Celsius.